Source: https://guthlabs.ai/docs/instruments/standard-enthalpy-of-reaction-h-f-calculator/

instrument / verified-clean

# Standard Enthalpy of Reaction (ΔH°f) Calculator

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/standard-enthalpy-of-reaction-h-f-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/standard-enthalpy-of-reaction-h-f-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/standard-enthalpy-of-reaction-h-f-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/standard-enthalpy-of-reaction-h-f-calculator/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Chemistry & Materials

**Tranche**: tranche-4

**Evidence ID**: t4-219

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The thermochemical formula is valid, but the product name, output basis, standard-state definition, phase requirements, and unit handling must be clarified before release. The honest label should be Standard Enthalpy of Reaction (ΔH°rxn) Calculator.

### Formula and scope findings

- The formula ΔH°rxn = ΣnΔH°f(products) − ΣnΔH°f(reactants) is standard and correct when the equation is balanced and all species phases are specified.

- The instrument name is misleading: it computes standard enthalpy of reaction (ΔH°rxn), not standard enthalpy of formation (ΔH°f).

- The result unit is ambiguous: the calculation produces kJ per stoichiometric reaction as written, while the specification labels the output only as kJ/mol. A reporting basis must be defined, especially for equations with coefficients other than 1.

### Unit assumptions

- All ΔH°f inputs are in kJ/mol of species.

- Stoichiometric coefficients are dimensionless and refer to the balanced reaction as written; fractional coefficients are allowed.

- The reported result is kJ per mole of stoichiometric reaction as written unless a different normalization basis is explicitly selected.

- Each species must have a specified physical phase, such as (s), (l), (g), or (aq), because ΔH°f depends on phase.

- Standard-state conditions should be defined, conventionally 298.15 K and 1 bar, with the applicable standard states for each species.

- Elemental substances in their reference states have ΔH°f = 0, subject to the selected standard-state convention.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The extreme user-supplied formation enthalpies cause the plain JavaScript arithmetic result to overflow to +Infinity. The specification does not state finite-input validation or non-finite-output rejection. A secondary hazard is that the formula has no genuine branch switch, despite the branch-switch test requirement.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "balanced_equation": "CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)",
    "reactants": [
      {
        "species": "CH4(g)",
        "coefficient": 1,
        "delta_Hf_kJ_per_mol": -74.85
      },
      {
        "species": "O2(g)",
        "coefficient": 2,
        "delta_Hf_kJ_per_mol": 0
      }
    ],
    "products": [
      {
        "species": "CO2(g)",
        "coefficient": 1,
        "delta_Hf_kJ_per_mol": -393.51
      },
      {
        "species": "H2O(l)",
        "coefficient": 2,
        "delta_Hf_kJ_per_mol": -285.83
      }
    ]
  },
  "expected_outputs": {
    "delta_H_rxn_kJ_per_mol_reaction": -890.32
  },
  "working": "Products = 1×(−393.51) + 2×(−285.83) = −393.51 − 571.66 = −965.17 kJ. Reactants = 1×(−74.85) + 2×0 = −74.85 kJ. ΔH°rxn = −965.17 − (−74.85) = −965.17 + 74.85 = −890.32 kJ per mol reaction."
}
````

## Related workflows

[Reaction Energetics BenchΔH](<https://guthlabs.ai/docs/instrument-workflows/reaction-energetics/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`